Shear band and a non-pneumatic tire

ABSTRACT

A shear band comprising a three-dimensional spacer structure, wherein the three-dimensional spacer structure is formed from a first and second layer of material, each layer of material having first reinforcement members which extend in a first and direction, and second reinforcement members which extend in a second direction, wherein each layer of material is connected to each other by a plurality of connecting reinforcement members which extend in a third direction, wherein the shear band further comprises a first membrane layer located radially outward of the three-dimensional spacer structure. The invention further comprises a non-pneumatic tire which includes the above described shear band.

FIELD OF THE INVENTION

The present invention relates generally to vehicle tires andnon-pneumatic tires, and more particularly, to a shear band and anon-pneumatic tire.

BACKGROUND OF THE INVENTION

The pneumatic tire has been the solution of choice for vehicularmobility for over a century. The pneumatic tire is a tensile structure.The pneumatic tire has at least four characteristics that make thepneumatic tire so dominant today. Pneumatic tires are efficient atcarrying loads, because all of the tire structure is involved incarrying the load. Pneumatic tires are also desirable because they havelow contact pressure, resulting in lower wear on roads due to thedistribution of the load of the vehicle. Pneumatic tires also have lowstiffness, which ensures a comfortable ride in a vehicle. The primarydrawback to a pneumatic tire is that it requires compressed gasses. Aconventional pneumatic tire is rendered useless after a complete loss ofinflation pressure.

A tire designed to operate without inflation pressure may eliminate manyof the problems and compromises associated with a pneumatic tire.Neither pressure maintenance nor pressure monitoring is required.Structurally supported tires such as solid tires or other elastomericstructures to date have not provided the levels of performance requiredfrom a conventional pneumatic tire. A structurally supported tiresolution that delivers pneumatic tire-like performance would be adesirous improvement.

Non pneumatic tires are typically defined by their load carryingefficiency. “Bottom loaders” are essentially rigid structures that carrya majority of the load in the portion of the structure below the hub.“Top loaders” are designed so that all of the structure is involved incarrying the load. Top loaders thus have a higher load carryingefficiency than bottom loaders, allowing a design that has less mass.

The purpose of the shear band is to transfer the load from contact withthe ground through tension in the spokes or connecting web to the hub512, creating a top loading structure. When the shear band deforms, itspreferred form of deformation is shear over bending. The shear mode ofdeformation occurs because of the inextensible membranes located on theouter portions of the shear band. Prior art non-pneumatic tire typicallyhave a shear band made from rubber materials sandwiched between at leasttwo layers of inextensible belts or membranes. The disadvantage to thistype of construction is that the use of rubber significantly increasesthe cost and weight of the non-pneumatic tire. Another disadvantage tothe use of rubber is that is generates heat, particularly in the shearband. Furthermore, the rubber in the shear band needs to be soft inshear, which makes it difficult to find the desired compound.

Thus an improved non-pneumatic tire is desired that has all the featuresof the pneumatic tires without the drawback of the need for airinflation is desired.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood through reference to thefollowing description and the appended drawings, in which:

FIG. 1 is a perspective view of a first embodiment of a non-pneumatictire of the present invention;

FIG. 2A is a cross-sectional view of a second embodiment of a shear bandand outer tread;

FIG. 2B is a cross-sectional view of a third embodiment of a shear bandand outer tread;

FIG. 3A is a perspective view of a first embodiment of an openthree-dimensional fabric structure, and FIG. 3B illustrates variouspossible configurations of the cross-members;

FIG. 4A is a perspective view of a second embodiment of a closed type ofthree-dimensional fabric structure, and FIG. 4B illustrates variouspossible configurations of the fabric cross-members;

FIG. 5 is a perspective view of a third embodiment of athree-dimensional fabric structure;

FIG. 6 is a perspective view of a fourth embodiment of athree-dimensional fabric structure;

FIG. 7 is a perspective view of a fifth embodiment of athree-dimensional fabric structure;

FIG. 8 is a perspective view of a sixth embodiment of athree-dimensional fabric structure;

FIG. 9 is a perspective view of a seventh embodiment of athree-dimensional fabric structure;

FIG. 10 is a perspective view of an eighth embodiment of athree-dimensional fabric structure;

FIG. 11 is a perspective view of a ninth embodiment of athree-dimensional fabric structure; and

FIG. 12 is the deflection measurement on a shear band from a force F.

DEFINITIONS

The following terms are defined as follows for this description.

“Auxetic material” means a material that has a negative Poisson's ratio.

“Equatorial Plane” means a plane perpendicular to the axis of rotationof the tire passing through the centerline of the tire.

“Free area” is a measure of the openness of the fabric per DIN EN 14971,and is the amount of area in the fabric plane that is not covered byyarn. It is a visual measurement of the tightness of the fabric and isdetermined by taking an electronic image of the light from a light tablepassing through a six inch by six inch square sample of the fabric andcomparing the intensity of the measured light to the intensity of thewhite pixels.

“Inextensible” means that a given layer has an extensional stiffnessgreater than about 25 Ksi.

“Knitted” is meant to include a structure producible by interlocking aseries of loops of one or more yarns by means of needles or wires, suchas warp knits and weft knits.

“Three-dimensional spacer structure” means a three-dimensional structurecomposed from two outer layers of fabric, each outer layer of fabrichaving reinforcement members (such as yarns, filaments or fibers) whichextend in a first and second direction, wherein the two outer layers areconnected together by reinforcement members (yarns, filaments or fibers)or other knitted layers that extend in a defined third direction.

“Woven” is meant to include a structure produced by multiple yarnscrossing each other at right angles to form the grain, like a basket.

DETAILED DESCRIPTION OF THE INVENTION

A first embodiment of a non-pneumatic tire 100 of the present inventionis shown in FIG. 1. The tire of the present invention includes aradially outer ground engaging tread 200, a shear band 320,330, and aconnecting web 500. The tire tread 200 may include elements such asribs, blocks, lugs, grooves, and sipes as desired to improve theperformance of the tire in various conditions. The connecting web 500may have different designs, as described in more detail, below. Thenon-pneumatic tire of the present invention is designed to be a toploading structure, so that the shear band 320,330 and the connecting web500 efficiently carry the load. The shear band 320,330 and theconnecting web are designed so that the stiffness of the shear band isdirectly related to the spring rate of the tire. The connecting web isdesigned to be a stiff structure when in tension that buckles or deformsin the tire footprint and does not compress or carry a compressive load.This allows the rest of the connecting web not in the footprint area theability to carry the load, resulting in a very load efficient structure.It is desired to allow the shearband to bend to overcome road obstacles.The approximate load distribution is preferably such that approximately90-100% of the load is carried by the shear band and the upper portionof the connecting web, so that the lower portion of the connecting webcarry virtually zero of the load, and preferably less than 10%.

Shear Band

The shear band 320,330 is preferably an annular structure that islocated radially inward of the tire tread 200 and functions to transferthe load from the bottom of the tire which is in contact with the groundto the spokes and to the hub, creating a top loading structure. Thisannular structure is called a shear band because the preferred form ofdeformation is shear over bending.

A first embodiment of a shear band 320 is shown in FIG. 2A, and iscomprised of an open three-dimensional spacer structure 400, shown inFIG. 3A. The three-dimensional spacer structure 400 may be positionedbetween a first and second layer of gum rubber 331,341 (not shown toscale). The gum rubber 331,341 may be as thick as desired. Thethree-dimensional spacer structure 400 is a type of structure that has afirst and second layer of fabric 460,470, wherein each layer of fabricis formed from a plurality of first reinforcement members 462 thatextend in a first or weft direction and a plurality of secondreinforcement members 464 which extend in a second or warp direction.The first and second reinforcement members 462,464 may be perpendicularto each other as shown, or crossed at a desired angle. As shown in FIG.3A, the reinforcement members 462 are interlaced or interwoven with thereinforcements 464. The first and second reinforcement layers may beknitted, woven, nonwoven, interlaced or non-interlaced. The first andsecond layers 460,470 of fabric are preferably oriented parallel withrespect to each other and are interconnected with each other byreinforcement connecting members 480,490 that extend in a third or piledimension. The perpendicular distance between the connecting layers460,470 or Z direction dimension of the three-dimensional structure isin the range of about 2 millimeters to about 25 millimeters, morepreferably about 3-10 millimeters, and even more preferably in the rangeof 5-10 mm

The three-dimensional spacer structure 400 may have differentarrangement of the reinforcement connecting members as shown in FIG. 3B.

The three-dimensional fabric structure 400 is preferably oriented in theshear band so that the first and second layers 460,470 are aligned inparallel relation with the axial direction. The three-dimensional fabricstructure 400 has a substantial Z dimension thickness which ispreferably aligned with the radial direction of the non-pneumatic tire.The open three-dimensional fabric structure 400 thus comprises aplurality of connecting members 480,490 which form open cells 495. Theopen cells 495 in the first embodiment remain empty. As shown in FIG.2A, the axial width of the connecting members 480,490 is less than theaxial width L of the shear band. The shear band further includescavities 481 located at the lateral ends of the shear band wherein theconnecting members are absent. The cavities 481 may be filled withrubber, elastomer or other material of a desired stiffness in order totune the stiffness of the tire. The cavity axial width may be adjustedfrom 0 to 30% of the shear band axial width L.

The reinforcement member or reinforcement connecting member may compriseone or more yarns, wire, one or more filaments, one or more fibers, orone or more reinforcement cords. The reinforcement member orreinforcement cross member may be formed of glass fiber, carbon fiber,basalt fibers, organic fibers, nylon, aramid, polyester, steel or metalwire, or combinations thereof. The reinforcements 464 may be oriented+/−15 degrees or less with respect to the tire equatorial plane, andmore preferably +/−10 degrees or less with respect to the tireequatorial plane.

Preferably, the three-dimensional fabric structure 400 and/orreinforcement member is treated with an RFL adhesive, which is awell-known resorcinol-formaldehyde resin/butadiene-styrene-vinylpyridine terpolymer latex, or a blend thereof with a butadiene/styrenerubber latex, that is used in the tire industry for application tofabrics, fibers and textile cords for aiding in their adherence torubber components (for example, see U.S. Pat. No. 4,356,219.) Thereinforcement members may be single end dipped members (i.e., a singlereinforcement member is dipped in RFL adhesive or adhesion promotor.)

The three-dimensional fabric structure 400 may have a density in therange of 700-1000 gram/meter2 as measured by DIN 12127. The compressionstiffness of the three-dimensional fabric structure 400 may range from50 to 600 kPa as measured by DIN/ISO 33861, and more preferably rangefrom 100 to 250 kPa.

The axial spacing S of the reinforcement connecting members 480 as shownin FIG. 3B may also be adjusted in order to control the stiffness of theshear band. The Spacing S may range from 3 mm to 8 mm.

The shear band is comprised of the three-dimensional spacer structure400 and may optionally include a first membrane layer 335. The firstmembrane layer 335 is preferably inextensible, and preferably locatedradially outward of the three-dimensional spacer structure 400. Theshear band may further comprise a second optional membrane layer 340that is arranged in parallel with the first membrane layer 335. If twomembrane layers are utilized to form the shear band, it is preferredthat the membrane layers 335,340 are separated by the three-dimensionalspacer structure 400 so that the three-dimensional spacer structure islocated between the layers. Preferably, a layer of gum rubber 331,341separates the three-dimensional spacer structure 400 from each membranelayer 335,340. The first and optional second membrane layers 335,340each have reinforcement members or cords that are oriented at an anglein the range of 0 to about +/−10 degrees relative to the tire equatorialplane. Preferably, the angle of the reinforcement cords of the firstlayer is in the opposite direction of the angle of the reinforcementcords in the second layer. It is additionally preferred that thereinforcement member or cords are inextensible.

FIG. 2B illustrated a second embodiment of the shear band 330 of thepresent invention. The second embodiment is the same as the firstembodiment shown in FIG. 2A, except for the following differences. Thefirst and second membrane layers 335,340 each have reinforcement cords331,341 that are spaced apart a distance SS. The distance SS may varyfrom 3-20 mm. The reinforcement cords are preferably brass coated steelwire, for example 2×0.295 HT or WL steel cords. The shear band furthercomprises a plurality of interwoven reinforcement members 493 that areinterwoven around the three-dimensional spacer reinforcement members 464of layer 460 and the nearest reinforcement cords 331 of the adjacentmembrane layer 335. Thus, the interwoven reinforcement members 493extends in the axial direction and interconnects the membrane layer 335with the radially outer shear band layer 460. Likewise, the interwovenreinforcement member 494 connects the radially inner three-dimensionalspacer structure layer 470 and the second membrane layer 340. Theinterwoven reinforcement members may be single end dipped members (i.e.,a single reinforcement member is dipped in RFL adhesive.)

Any of the above described embodiments of the shear band may utilize thethree-dimensional structure shown in FIG. 4A. The three-dimensionalstructure 350 shown in FIG. 4A includes a first knitted or woven layer360 of fabric, and a second knitted or woven layer 370 of fabric. Thefirst and second layers are joined together by a plurality of crossmembers 380. The cross members 380 are connected to the first and secondwoven layers at a 90 degree angle. The first and second woven layers360,370 are preferably oriented in parallel relation to the axialdirection. Alternatively, the first and second woven layers may beconnected as shown in FIG. 4B, with variable connecting lengths, orvariable connecting angles or in multiple layers.

Any of the above described embodiments of the shear band may utilize thethree-dimensional structure shown in FIGS. 5-7, which illustrate variousdifferent configurations of the cross members 480, 490.

Any of the above described embodiments of the shear band may utilize thethree-dimensional structure shown in FIG. 8. The three-dimensionalstructure 500 comprises a first woven layer 560 of fabric, and a secondwoven layer 570 of fabric. The first and second layers are joinedtogether by a plurality of cross members 580 formed in the shape of an“8”.

Any of the above described embodiments of the shear band may utilize thethree-dimensional structure shown in FIG. 9 or 10. The three-dimensionalstructure 700 of FIG. 9 comprises a first knit layer 760 of fabric, anda second knit layer 770 of fabric. The first and second layers arejoined together by a plurality of knitted spacing threads 780. The firstand second layers 760,770 each have openings formed by a plurality ofmeshes, and wherein channels are formed between the knit fabric layersand are free of spacer threads.

Any of the above described embodiments of the shear band may utilize thethree-dimensional structure shown in FIG. 11. The three-dimensionalstructure 800 comprises two or more deck layers 810,820. Thethree-dimensional structure 800 has a first woven layer 860 of fabric, asecond woven layer 870 of fabric, and a middle woven layer 880. Thefirst and middle layers 860,880 are joined together by a plurality ofcross members 890. The second and middle layers 870,880 are also joinedtogether by a plurality of cross members 895. The cross members 890,895may be angled or curved as shown in FIGS. 4-8.

Any of the above described embodiments of the three-dimensional fabricstructure may have a density in the range of 700-1000 gram/meter2 asmeasured by DIN 12127. The compression stiffness of thethree-dimensional fabric structure may range from 50 to 600 kPa asmeasured by DIN/ISO 33861, and more preferably range from 100 to 250kPa.

It is additionally preferred that the lateral ends of the shear band betapered, so that the radial thickness of the center of the shear band isgreater than the thickness at the outer ends of the shear band.

Shear Band Properties

The shear band has an overall shear stiffness GA. The shear stiffness GAmay be determined by measuring the deflection on a representative testspecimen taken from the shear band. The upper surface of the testspecimen is subjected to a lateral force F as shown below. The testspecimen is a representative sample taken from the shear band and havingthe same radial thickness as the shearband. The shear stiffness GA isthen calculated from the following equation:

GA=F*L/ΔX, where F is the shear load, L is the shear layer thickness,and delta X is the shear deflection.

The shear band has an overall bending stiffness EI. The bendingstiffness EI may be determined from beam mechanics using the three pointbending test. It represents the case of a beam resting on two rollersupports and subjected to a concentrated load applied in the middle ofthe beam. The bending stiffness EI is determined from the followingequation: EI=PL3/48*ΔX, where P is the load, L is the beam length, andΔX is the deflection.

It is desirable to maximize the bending stiffness of the shearband EIand minimize the shear band stiffness GA. The acceptable ratio of GA/EIwould be between 0.01 and 20, with an ideal range between 0.01 and 5. EAis the extensible stiffness of the shear band, and it is determinedexperimentally by applying a tensile force and measuring the change inlength. The ratio of the EA to EI of the shearband is acceptable in therange of 0.02 to 100 with an ideal range of 1 to 50.

The shear band 300 preferably can withstand a maximum shear strain inthe range of 15-30%.

The shear band preferably has a GA/EI in the range of 0.01 to 20, or aEA/EI ratio in the range of 0.02 to 100, or a spring rate in the rangeof 20 to 2000, as well as any combinations thereof. More preferably, theshear band has a GA/EI ratio of 0.01 to 5, or an EA/EI ratio of 1 to 50,or a spring rate of 170 lb./in, and any subcombinations thereof. Thetire tread is preferably wrapped about the shear band and is preferablyintegrally molded to the shear band.

Connecting Web

The non-pneumatic tire of the present invention further includes aconnecting web 500 as shown in FIG. 1. The connecting web preferablycomprises a plurality of circumferentially aligned spokes 510 thatextend from an inner radius to an outer radius. The spokes arepreferably oriented in the radial direction. The spokes may be curved orstraight. Preferably, the non-pneumatic tire comprises two sets ofcircumferentially aligned spokes. The spokes may have differentcross-sectional designs. The spokes functions to carry the loadtransmitted from the shear layer. The spokes are primarily loaded intension and shear, and carry no load in compression. Each spoke asdescribed herein has an axial thickness A that is substantially lessthan the axial thickness AW of the non-pneumatic tire. The axialthickness A is in the range of 5-20% of AW, more preferably 5-10% AW. Ifmore than one disk is utilized, than the axial thickness of each diskmay vary or be the same.

The spokes 510 preferably extend in the radial direction. The spokes 510are designed to bulge or deform in the radial direction. When thenon-pneumatic tire is loaded, the spokes will deform when passingthrough the contact patch with substantially no compressive resistance,supplying zero or insignificant compressive force to load bearing. Thepredominant load of the spokes is through tension and shear, and notcompression.

The spokes are preferably formed of an elastic material such as rubberor a thermoplastic elastomer. The radial spokes are designed such thatthe spokes have a low resistance to radial deformation and a higherresistance to the lateral deformation of the tire.

If the material selected is a thermoplastic elastomer, then it ispreferred to have the following properties. The tensile (Young's)modulus of the disk material is preferably in the range of 45 MPa to 650MPa, and more preferably in the range of 85 MPa to 300 MPa, using theISO 527-1/−2 standard test method. The glass transition temperature isless than −25 degree Celsius, and more preferably less than −35 degreeCelsius. The yield strain at break is more than 30%, and more preferablymore than 40%. The elongation at break is more than or equal to theyield strain, and more preferably, more than 200%. The heat deflectiontemperature is more than 40 degree C. under 0.45 MPa, and morepreferably more than 50 degree C. under 0.45 MPa. No break result forthe Izod and Charpy notched test at 23 degree C. using the ISO179/ISO180 test method. Two suitable materials for the disk iscommercially available by DSM Products and sold under the trade nameARNITEL PL 420H and ARNITEL PL461.

Applicants understand that many other variations are apparent to one ofordinary skill in the art from a reading of the above specification.These variations and other variations are within the spirit and scope ofthe present invention as defined by the following appended claims.

What is claimed:
 1. A shear band comprising a three-dimensional spacer structure, wherein the three-dimensional spacer structure is formed from a first and second layer of material, each layer of material having first reinforcement members which extend in a first direction, and second reinforcement members which extend in a second direction, wherein the first and second layer of material are connected to each other by a plurality of connecting reinforcement members which extend in a third direction, wherein the shear band further comprises a first membrane layer, and wherein the shear band further comprises a first set of interwoven reinforcement members that are interwoven around the reinforcement members of the first layer of the three-dimensional spacer structure and a reinforcement cord of the first membrane layer.
 2. The shear band of claim 1 further comprising a second membrane layer located radially inward of the three-dimensional spacer structure.
 3. The shear band of claim 1 wherein the reinforcement cord of the first membrane layer is oriented at an angle in the range of +/−20 degrees with respect to the tire equatorial plane.
 4. The shear band of claim 2 wherein the second membrane layer has reinforcement cords that are oriented at an angle in the range of +/−20 degrees with respect to the tire equatorial plane.
 5. The shear band of claim 1 wherein the reinforcement cords are spaced apart a distance SS which ranges from 3 to 10 mm.
 6. The shear band of claim 1 wherein the reinforcement cords are inextensible.
 7. The shear band of claim 1 wherein the first direction is aligned with the circumferential direction of the shear band.
 8. The shear band of claim 1 further comprising a second set of interwoven reinforcement members that are interwoven around the reinforcement members of the radially inner layer of the three-dimensional spacer structure and a reinforcement cord of the radially inner membrane layer.
 9. The shear band of claim 8 wherein the interwoven reinforcement members extend in the axial direction.
 10. The shear band of claim 1 wherein the first and second layers are parallel with respect to each other.
 11. The shear band of claim 1 wherein the connecting reinforcement members extend in a third direction, and the third direction is aligned with the radial direction of the shear band.
 12. The shear band of claim 1 wherein the first and second layers are separated by a distance Z in the range of 2 to 25 millimeters.
 13. The shear band of claim 1 wherein the three-dimensional spacer structure is formed of an auxetic material.
 14. A non-pneumatic tire comprising a ground contacting annular tread portion; and a shear band formed from any of the claims 1-7 and 8-13. 